The present invention relates to an image processing method for effecting a diversification processing, e.g., shadowing, to a dot-matrixed bit-map image data.
Hitherto, a method has been proposed for forming a modified letter, e.g., a bordered letter, shadowed letter and so forth, by effecting a diversification processing on dot-matrixed letter data. According to this method, first and second data are formed by incrementing or decrementing the coordinates of the points where the levels of the dot signals are changed from white to black and vice versa in the dot-matrixed letter data both in the direction of main scan and in the direction of auxiliary scan perpendicular to the main scan. Then, a logical sum or logical product of these first and second data is further logically processed together with the dot-matrixed letter data, whereby a modified letter is formed. Thus, the diversification processing for forming a modified letter relies upon shifting of the coordinates of the contour of the dot-matrixed letter up and down and to the left and right. This method is disclosed in, for example, Japanese Patent Application No. 145986/1983.
The above-mentioned method, however, is applied only to letter image which permits an easy pickup of contour coordinate data, and cannot be applied to bit-map image data. Conventionally, therefore, a diversification processing of the image data has been conducted by forming a plurality of data by shifting the image data in a dot-by-dot fashion and determining logical sum or logical product of such data.
Thus, in the known diversification process for the bit-map image data, the image data is shifted only in dot-by-dot manner, so that the processing times increases in proportion to increase in the amount of processing, which is inconvenient particularly when the amount of processing is large.